Method of modification of the color of gems

ABSTRACT

An improved method of producing gems of changed color wherein the gems are placed in contact with a particulate radioactive material. Radioactive contamination of the gem is effectively removed by immersion in a liquid bath which dissolves the attachment of radioactive solids to the gems, and acid is a preferred liquid. Preferably the irradiated gems are first subjected to a mild abrasive action to remove most of the radioactive material. The irradiation, abraiding, and dissolving steps are preferably all done in a single generally airtight enclosure.

United States Patent [72] Inventor John C. Haynes 12 E. Park Place, Newark, Ohio 43055 [21] Appl. No. 733,274 [22] Filed May 31, 1968 [45] Patented Oct. 26, 1971 [54] METHOD OF MODIFICATION OF THE COLOR OF GEMS 12 Claims, No Drawings [52] US. Cl ..204/157.1 H 51 1nt.C1 B0lj 1/10 [50] Field of Search 204/157.1

[56] References Cited UNITED STATES PATENTS 2,945,793 7/1960 Dugdale 204/157. 1

Primary Examiner-Howard S. Williams Attorney-William P. Hickey ABSTRACT: An improved method of producing gems of changed color wherein the gems are placed in contact with a particulate radioactive material. Radioactive contamination of the gem is effectively removed by immersion in a liquid bath which dissolves the attachment of radioactive solids to the gems, and acid is a preferred liquid. Preferably the irradiated gems are first subjected to a mild abrasive action to remove most of the radioactive material. The irradiation, abraiding, and dissolving steps are preferably all done in a single generally airtight enclosure.

METHOD OF MODIFICATION OF THE COLOR OF GEMS BACKGROUND OF THE INVENTION In an article published in 1909, Sir Walter Crookes described a process for the coloration of diamonds. The process used by Crookes comprised the immersion of the diamond in liquid radium bromide for an extended period of time. The diamonds as produced by Crookes were radioactive even after prolonged treatment with strong nitric acid and potassium chlorate and so these gems could not be used near or about the person. The colored diamonds created by Crookes, therefore, were substantially worthless except as a curiosity.

The interest in colored gems and particularly diamonds has been prolonged and intense and the next significant efiort at coloring diamonds involved the irradiation of the gems by means of a cyclotron. The colored gems which were produced using a cyclotron varied from bluish green to dark shades of yellow and tended to have an umbrella effect around the cullet or a dark ring around the girdle depending upon whether the stones were bombarded from the cullet side or the crown side. Stones colored by the cyclotron produce a spectrograph having a 5,920 angstrom unit absorption line that is not produced in the spectrograph of natural stones which are correspondingly colored. The cyclotron colored stones likewise show absorption lines of 4,980 and 5,040 angstrom units with the 4,980 line being stronger than the 5,040 line. Naturally occurring green-colored diamonds, however, have a 5,040 line which is stronger than the 4,980 line. The stones produced by the cyclotron do not have the uniform color distribution of a natural stone. The coloration of gems by means of a cyclotron has not proven practical because of the poor results, the great expense, and the limited time available on the few existing cyclotron facilities.

A further process which has been used for the coloring of diamonds has involved the placing of the stones to be colored in a tube in a nuclear reactor. The colored stones which have been created have the 5,920 angstrom unit absorption line that is not characteristic of naturally occurring diamonds, and in addition have 4,980 and 5,040 lines of approximately equal strength, whereas the naturally occurring diamonds have a 5,040 line that is stronger than the 4,980 line. Because the diamonds are subjected to intense radiation in the reactor, the lattice structure of the diamond is weakened so that the cohesive energy of the diamond may be reduced by 40 percent, and the hardness by as much as 75 percent. This same decrease in strength occurs in the cyclotron-treated diamonds due to intense radiation and heat. Because it is difficult to accurately control the length of time of the irradiation in a nuclear reactor, the diamonds cannot be treated to predetermined shades of color and the treatment, therefore, is varied and nonuniform. More important, however, nuclear reactor treated diamonds tended more to the yellow side than to the green side, and those green stones which are produced are not of optimum beauty. Green stones which are not of optimum beauty are less salable. The cyclotron and nuclear reactor processes, therefore, tend to provide only a small percentage of stones of the most highly desired coloration. Even then, cyclotron or nuclear reactor colored stones have differences which are detectable from the naturally occurring stones.

An object of the present invention, therefore, is the provision of a new and improved method of changing the color of gems which will leave the gems nonradioactive, so that they can be worn on the person.

A further object of the present invention is the provision of a new and improved process of coloring gems which produces a colored gem that is similar to the naturally occurring gems in all respects and is, therefore, undistinguishable from the naturally occurring colored gem.

A still further object of the present invention is the provision of a new and improved method of coloring gems that is highly controllable and wherein the color of the gem can be changed to any desired condition.

Further objects and advantages of the invention will become apparent to those skilled in the art from the following discussion and description of the preferred embodiments.

SUMMARY OF THE INVENTION According to the present invention, the gems whose color is to be changed are placed directly in contact with, and preferably surrounded by, a radioactive material giving off a desired type of radiation. The radioactive material used must be a solid that does not sublime or liquefy under the treating conditions, and is preferably a paniculate matter, so that the particles thereof can be easily caused to engage and preferably surround all surfaces of the gem to be treated. After a desired length of time of being embedded in the particulate radioactive material, the gems are removed and subjected to the action of a liquid which will dissolve the attachment of the radioactive material to the surface of the gem. Where this attachment is not produced by a film former, etc., but is a direct contact of the radioactive material with the surface of the gem, and where the gem withstands the action of an acid, the radioactive material is dissolved away by an acid. The gems are preferably subjected to a series of clean acid baths followed by water rinses. It has been found that this treatment removes all radioactivity, such that residual radioactivity of the gem is well below the requirement specified by the Atomic Energy Commission, Code of Federal Regulations, Title l0, Chapter I, Part 20.

Prior to immersion in the first acid bath, and after the gems are removed from the radioactive material, they are preferably subjected to the action of an abrasive, however mild, in order to physically remove most of the clinging radioactive "wipe" as a solid so that it can be more easily reclaimed. In the case of diamonds, any cheap abrasive can be used including sand. With other gems, a more mild abrasive such as talc may be desired.

The process is preferably carried out in an airtight enclosure having mechanical arms manipulated from the outside of the enclosure for moving the gems into and out of a container of the solid radioactive material, followed by moving the gem into and out of tumbler of abrasive such as sand, followed by moving the diamond into and out of an acid bath. The acid bath containing the diamond can be removed from the enclosure, but more preferably, however, the diamond is removed from the first acid bath and placed in a container of clean acid which is then removed from the enclosure. The second container of acid is then preferably subjected to ultrasonic vibrations following which the diamond is removed and placed in a third acid bath which is also subjected to ultrasonic vibration, following which it is removed and washed with water and detergent. The gems are then tested for radioactivity by means of a Geiger counter or other sensing instrument, and if no de tectable radiation is present, the diamond is ready for mounting and use.

The irradiated diamonds will, when irradiated with alpha radiation, be an emerald green, the color of which can be lightened somewhat by heating above approximately 600 F. At 800 F., the color can be changed to a chartreuse; at l,000 F., it can be changed into a very light yellow, and at temperatures up to l,800 F., can be progressively darkened to shades of gold. In those instances when the degree of coloration is lighter than desired, the gem can be reirradiated using the process above described to add green coloration. If still darker shades of yellow are desired, the gem can be retreated. Very precise shades can be obtained by one or two stages of retreatment, and because the process is so workable and controllable, substantially any gem, regardless of original color, can be changed into a desired shade of green or yellow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the principles of the present invention, a new and improved method is provided for changing the color of gems, which method produces gems having no appreciable residual radioactivity and, therefore, can be worn in direct contact with the person. Using the methods of the present invention, the gems can be irradiated with any known type of radiation including alpha, beta, gamma, slow-moving neutrons, fast-moving neutrons, dcuterons, positrons, and/or mesons. it will be understood, therefore, that the method or methods of the present invention are applicable to the treatment of all types of gems. One preferred embodiment of the invention involves the method of changing the color of diamonds into an emerald green indistinguishable from that of naturally occurring diamonds, and later if desired into shades of yellow.

According to a further aspect of the invention, it has been found that the naturally occurring shades of green diamonds are best produced by a radiation that is substantially pure alpha and which is substantially devoid of gamma or beta radiation. Any charged particle, however, can be used with great efi'ect, and gamma or neutrons can be used with a lesser effect. The diamonds which are produced according to the embodiment about to be described have a color which is an improvement over radium-treated diamonds by reason of the substantial elimination of gamma radiation.

EXAMPLE 1 In the preferred embodiment about to be described, a diamond to be colored is placed into a small container of Americium 241 oxide. The container is located in a substantially airtight enclosure called a Glove Box," and the diamond is placed therein by means of mechanical fingers remotely controlled from a position outside of the "Glove Box." The container is shaken sufficiently to allow the diamond to embed in the Americium oxide powder, the particles of which pass through a hundred-mesh screen. The diamond is left in the Americium powder for a period exceeding 2 days, and usually from 7 days to 2 weeks. in the particular treatment being described, a 50-point commercial diamond was embedded in the Americiurn oxide powder for 7 days and was thereafter removed from the Americium oxide by the mechanical fingers, and placed in a glass jar containing sand. A cover was placed on the jar and the jar tumbled for several minutes after which the diamond was removed by the mechanical fingers. The diamond was then placed in a container having approximately 25 cc. of concentrated nitric acid therein, and was let stand for approximately l minutes. Thereafter, the acid was poured into another container and the diamond dropped into a second container of approximately 25 cc. of radioactive clean concentrated nitric acid. The second container of nitric acid was then removed from the Glove Box" and ultrasonically agitated for approximately minutes. The second bath of acid was poured from the container and the diamond dropped into a third container of 25 cc. of radioactive clean concentrated nitric acid, and again ultrasonically vibrated for IS minutes. The third bath of acid was then poured out of the container and the diamond dropped into a be Water was then added to the beaker and the diamond washed to remove the acid. The diamond was then removed from this water, and was scrubbed with water and detergent to remove all acid, soil, etc. When tested with a Geiger counter, no radioactivity was found to exist in the diamond.

The diamond produced as above described, was an emerald green. Tl-le spectrograph of the diamond exhibited 4,980 and 5,040 angstrom absorption bands with the 5,040 line being darker, and there was an absence of a 5,920 angstrom unit absorption band. The spectrograph was, therefore, like the spectrograph of natural occurring diamonds and unlike that of cyclotron or nuclear reactor treated diamonds. The stone was as bright as naturally occurring diamonds, and lacked the dull appearance characteristic of nuclear reactor treated diamonds.

The emerald green color of the diamond produced as above described was changed into a very light yellow by placing the diamond in an electric heated air furnace at 1,000" P. for onehalf hour. Prior to being placed in the furnace, the diamond was coated with boric acid-alcohol paste to prevent oxidation. When removed from the furnace and cooled, the color of the diamond had been changed to a very light yellow. Others similarly radiated at 600 F. were made a lighter shade of green; others heated to 800 F. were changed to a Chartreuse, and those heated at l,800 F. were changed to a gold color.

The diamond prepared as above described was a completely marketable yellow stone. In order to determine if the color could be darkened, the very light yellow diamond was again irradiated, using the same procedure above described, for an additional 7-day period, and thereafter tumbled and acid treated in the same manner described above. The diamond was then washed, coated with boric acid paste, heated in a furnace at l,800 F. for one-half hour and was thereby changed into a brilliant shade of gold. The gold diamond has all the luster and hardness of naturally occurring similarly colored stones, and was not weakened as are the stones produced by the cyclotron or the nuclear reactor treated stones. The stone likewise was free of detectable radioactivity.

As previously indicated, other radioactive materials can be used to color diamonds, using gamma radiation, fast-moving neutrons, deuterons, positrons, etc. These types of radiation are not used, however, in the preferred method of making green or yellow diamonds. in the preferred method of making green diamonds, only those radioactive materials giving off substantially pure alpha radiation are preferred. Suitable examples of these materials are Plutonium 238, Americium 24l, and Polonium 210 diluted with an inert granular material.

Those materials which are used, however, should remain in a solid state and not transform into a vapor or liquid. Poloniurn, for instance, volatilizes at 55 C. and is preferably not used as a metal at room temperature. High-melting salt of Polonium 210 such as a sulfate, etc., can be used.

EXAMPLE 2 A 50-point cut diamond is embedded in a granular Plutonium 238, oxide for 14 days using the procedure outlined above. After washing with nitric acid as above described, the diamond has no detectable radiation, and has a green color whose spectograph corresponds with that of the natural occurring green diamonds.

Diamonds can be changed to a blue color by using beta radiation and the same general process outlined above.

EXAMPLE 3 By way of example, a 50-point cut diamond is embedded in a Strontium oxide granular material of minus mesh for 14 days and is cleaned using muriatic acid in the procedure outlined above. After cleaning, the diamond has no detectable radiation and has a blue color. Other beta emitters which can be used are Antimony 125, Tritrium, lritrium 90, Cesium 134, Cesium 137, Barium l39, Beryllium l0, Cobalt 60, Nickel 53, Promethium l47, Strontium 90, Thallium 204, etc. Here again, the radioactive materials must be in a solid form having substantially no vapor pressure. Any suitable oxide or salt of these materials can be used. in the case of Tritrium, it may be used as a hydride of beryllium or aluminum.

While gamma radiation is not a preferred radiation for coloring gems, gamma emitters can be used in the process outlined above to achieve an improvement over that obtained when gamma emitters are used in prior art processes. Suitable examples of gamma emitters are: Cobalt 60, Cesium 137, Iron 55. Magnesium 54, Mercury 203, Barium 133, etc.

Likewise, fast-moving neutrons are not a preferred form of radioactivity but when used in the process above described an advantage can be had over that used in the prior art processes. Suitable examples of fast-moving neutron sources are obtained when Americium 24 l as for example, in an oxide state, is immersed in the mixture. Similarly, a fast-moving neutron source can be obtained using a mixture of powders of Plutonium 238, and beryllium or a mixture of Polonium 210 sulfate. and beryllium powder.

Similarly, though not preferred, an advantage is had over prior art processes using neutrons, when the radioactive material is used in the method outlined above.

Similarly, in those instance when positron bombardment is desired, an advantage is had when used in the method outlined above as opposed to when used in the prior art processes. Suitable examples of positron emitters are: Sodium 22, Aluminum 26, Lanthanum 138, etc.

While the invention has been thus far described as having particular advantages in the changing of the color of diamonds, it will be understood that it likewise can be used to change the color of other stones.

EXAMPLE 4 A 2-carat piece of quartz was embedded in Americium 241 oxide for 14 days using the procedure described in example 1. The stone was devoid of detectable radiation after the acid cleaning baths and had a gray color.

EXAMPLE 5 A topaz gem was embedded in Americium 241 oxide for 14 days using the procedure described in example 1. It likewise was devoid of detectable radioactivity after acid treatment and had a pinkish-yellow color.

Other examples of stones which can be treated are: zircon, garnet, corundum, chrysoberyl, spinel, perodet, spodumene, towmaline, etc.

Prior to the present invention, it was not obvious that gems placed directly in engagement with a radioactive material could be treated without leaving residual radioactivity in the gem. Since the present invention has demonstrated that this is possible, the reason for radioactivity in the prior art treated gems can now be postulated, although not previously known. It is believed that all gems have minute cracks in the crystal lattice which are open to the surface of the gem and that in many instances these cracks communicate with contaminating foreign materials. In the case of a diamond, the contamination materials may be graphite having an amorphous structure which is porous and absorbent. It is further believed that prior art radium treatments have caused radioactive liquid to penetrate these cracks, and that this liquid is never completely removed with subsequent liquid bath treatments.

in the process of the present invention, however, the radioactive particles including wipe" (a dust that collects on the surface of the radioactive emitter) does not penetrate the cracks but at best is lodged at the entrance to the crack. Wipe may also be held in place by grease or other films. By dissolving the attachment of these particles, be it the attaching film or be it the surface of the particle that is wedged into the cracks, the radioactive material is either dissolved away or loosened so that it may fall clear of the surface of the gem. Any remaining radioactive liquid is replaced by subsequent clean liquid long before it has a chance to penetrate the cracks in the surface of the gem. With the process of the present invention, the driving force for the radioactive material is outwardly from the gem, rather than into the gem, by reason of the concentration differences.

The reason why the gems produced by the present invention have improved color over those produced by the prior art processes can now also be postulated. in the case of the radium-treated gem, the gem is bombarded by a considerable amount of gamma radiation which penetrates the gem and increases the opacity of the gem throughout. This, therefore, causes the gem to lose luster. In addition, gamma radiation tends to produce the characteristic brown spots which are observed in radium-treated gems.

In the case of cyclotron-treated gems, the radiation is highly directional, such that some surfaces of the gem are more highly colored than others. In contrast, the coloration of the gems produced according to the present invention are subject to radiation uniformly from all sides, and in the case of alpha radiation, to a depth of a few mils beneath the surface of the gem. ln the case of the cyclotron, when alpha radiation is used, the parallel radiation changes the color of the surfaces nonunifonnly. In the ease of the cyclotron, when gamma or fast-moving neutrons, deuterons, etc., are used, the radiation goes completely through the stone, and the stone lacks brilliance. ln addition, these stones have the characteristic 5,920 angstrom unit absorptive line.

In the case of the nuclear reactor treated gems, the gems are again subjected to a variety of types of radiation, which completely penetrate the stone to cause the stone to have the characteristic 5,920 angstrom unit absorption line, lack luster, and have weakened structure.

While the invention has been described in considerable detail, 1 do not wish to be limited to the particular embodiments shown and described, and it is my intention to cover hereby all novel adaptations, modifications, and arrangements thereof which come within the practice of those skilled in the art to which the invention relates and which come within the preview of the following claims.

lclaim:

l. A method of changing the color of gems comprising: placing a gem to be treated in contact with particulate radioactive material selected from the group consisting of predominantly alpha and beta emitters without wet-dissolved radioactivity contacting the gem and for a sufficient period of time to effect a color change in the gem, removing the gem from the particulate radioactive material, and immersing the irradiated gem in a liquid which dissolves the attachment to the gem of the radioactive material, including its wipe.

2. The method of claim 1 wherein the liquid is an acid which dissolves the radioactive wipe.

3. The method of claim 2 including the step of: subjecting the gem to movement of a particulate abrasive material over its surface prior to immersion in the acid.

4. The method of claim 2 including the step of: removing the gem from a first acid bath and immersing it in one or more successive baths of radioactive clean acid.

5. The method of claim l wherein the gem is a diamond.

6. The method of claim 5 wherein the emitter is an alpha emitter and the diamond is exposed to the alpha emitter for a period of time to develop a 4,980 angstrom unit spectrographic absorption band, a 5,040 angstrom unit spectrographic absorption band that is stronger than the 4,980 band without developing an appreciable 5,920 angstrom unit spectrographic absorption band, said exposure not appreciably reducing the cohesive energy of the diamond and continuing until the crystal lattice of at least a surface layer of the diamond is modified to impart color.

7. The method of claim 6 wherein the radiation is from Americium 241.

8. The method of claim 6 wherein the radiation is from Plutonium 238.

9. The method of claim 5 wherein the radiation is from Strontium 90.

10. The method of changing the color of a gem comprising: introducing the gem to be treated into an enclosure having a vessel therein containing a particulate radioactive material from the group consisting of Americium 241, Plutonium 238, Polonium 210, Antimony 125, Tritrium, lritrium 90, Cesium 134, Cesium 137, Barium I39, Beryllium 10, Cobalt 60, Nickel 63, Promethium I47, Strontium and Thallium 204, placing the gem in the container and causing the gem to be engaged by the particulate radioactive material without wet-dissolved radioactivity contacting the gem, removing the irradiated gem from the container and placing it in a container of abrasive also located in the same enclosure, causing the abrasive to move over the surface of the gem to remove dry radioactive material, removing the gem from the abrasive and immersing the gem in a container of acid which dissolves the radioactive material and which is also located in the enclosure, and removing the gem from the enclosure for washing and drying.

ii. The method of claim 10 wherein the radioactive material contains atoms of Americium 24l and the gem is a diamond.

12. The method of claim 11 wherein the container of acid is subjected to ultrasonic vibration when the gem is immersed therein.

t i t i 

2. The method of claim 1 wherein the liquid is an acid which dissolves the radioactive wipe.
 3. The method of claim 2 including the step of: subjecting the gem to movement of a particulate abrasive material over its surface prior to immersion in the acid.
 4. The method of claim 2 including the step of: removing the gem from a first Acid bath and immersing it in one or more successive baths of radioactive clean acid.
 5. The method of claim 1 wherein the gem is a diamond.
 6. The method of claim 5 wherein the emitter is an alpha emitter and the diamond is exposed to the alpha emitter for a period of time to develop a 4,980 angstrom unit spectrographic absorption band, a 5,040 angstrom unit spectrographic absorption band that is stronger than the 4,980 band without developing an appreciable 5,920 angstrom unit spectrographic absorption band, said exposure not appreciably reducing the cohesive energy of the diamond and continuing until the crystal lattice of at least a surface layer of the diamond is modified to impart color.
 7. The method of claim 6 wherein the radiation is from Americium
 241. 8. The method of claim 6 wherein the radiation is from Plutonium
 238. 9. The method of claim 5 wherein the radiation is from Strontium
 90. 10. The method of changing the color of a gem comprising: introducing the gem to be treated into an enclosure having a vessel therein containing a particulate radioactive material from the group consisting of Americium 241, Plutonium 238, Polonium 210, Antimony 125, Tritrium, Iritrium 90, Cesium 134, Cesium 137, Barium 139, Beryllium 10, Cobalt 60, Nickel 63, Promethium 147, Strontium 90 and Thallium 204, placing the gem in the container and causing the gem to be engaged by the particulate radioactive material without wet-dissolved radioactivity contacting the gem, removing the irradiated gem from the container and placing it in a container of abrasive also located in the same enclosure, causing the abrasive to move over the surface of the gem to remove dry radioactive material, removing the gem from the abrasive and immersing the gem in a container of acid which dissolves the radioactive material and which is also located in the enclosure, and removing the gem from the enclosure for washing and drying.
 11. The method of claim 10 wherein the radioactive material contains atoms of Americium 241 and the gem is a diamond.
 12. The method of claim 11 wherein the container of acid is subjected to ultrasonic vibration when the gem is immersed therein. 